Organic Electroluminescent Materials and Devices

ABSTRACT

A compound of Formula Iwherein:ring B is a 5-membered heterocyclic ring, or a 6-membered carbocyclic ring;each of X1 and X2 is independently C, CR, or N, with at least one of them being C;each of X3-X11 is independently C, CR, or N, with at least one of them being N, and two adjacent of X3-X7 are carbon-fused to the shown moiety through the linkage indicated by the two squiggly lines;Y is selected from the group consisting of O, S, Se, NR′, CR′R″, and SiR′R″;each of RA and RB independently represents zero, mono, or up to a maximum allowed substitution to its associated ring;each of R, R′, R″, RA, and RB is independently a hydrogen or a substituent selected from the group consisting of —SiR1R2R3 or —GeR1R2R3, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, with at least one of RA or RB comprising —SiR1R2R3 or —GeR1R2R3;each of R1, R2, and R3 is independently selected from the group consisting of alkyl, aryl group, heteroaryl group, and combinations thereof; andany two substituents are optionally joined or fused to form a ring where chemically feasible.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/809,113, filed Feb. 22, 2019, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to compounds for use as hosts and devices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting diodes/devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Alternatively the OLED can be designed to emit white light. In conventional liquid crystal displays emission from a white backlight is filtered using absorption filters to produce red, green and blue emission. The same technique can also be used with OLEDs.The white OLED can be either a single EML device or a stack structure. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processable” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

SUMMARY

A compound of Formula I

wherein:

-   -   ring B is a 5-membered heterocyclic ring, or a 6-membered         carbocyclic ring;     -   each of X¹ and X² is independently C, CR, or N, with at least         one of them being C;     -   each of X³-X¹¹ is independently C, CR, or N, with at least one         of them being N, and two adjacent of X³-X⁷ are carbon-fused to         the shown moiety through the linkage indicated by the two         squiggly lines;     -   Y is selected from the group consisting of O, S, Se, NR′, CR′R″,         and SiR′R″;     -   each of R^(A) and R^(B) independently represents zero, mono, or         up to a maximum allowed substitution to its associated ring;     -   each of R, R′, R″, R^(A), and R^(B) is independently a hydrogen         or a substituent selected from the group consisting of —SiR¹R²R³         or —GeR¹R²R³, deuterium, halogen, alkyl, cycloalkyl,         heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy,         amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl,         alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester,         nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino,         and combinations thereof, with at least one of R^(A) or R^(B)         comprising —SiR¹R²R³ or —GeR¹R²R³;     -   each of R¹, R², and R³ is independently selected from the group         consisting of alkyl, aryl group, heteroaryl group, and         combinations thereof; and         any two substituents are optionally joined or fused to form a         ring where chemically feasible.

An OLED comprising the compound of the present disclosure in an organic layer therein is also disclosed.

A consumer product comprising the OLED is also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2 .

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2 . For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink jet and organic vapor jet printing (OVJP). Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processability than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the present invention may further optionally comprise a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment including moisture, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise a single layer, or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of electronic component modules (or units) that can be incorporated into a variety of electronic products or intermediate components. Examples of such electronic products or intermediate components include display screens, lighting devices such as discrete light source devices or lighting panels, etc. that can be utilized by the end-user product manufacturers. Such electronic component modules can optionally include the driving electronics and/or power source(s). Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of consumer products that have one or more of the electronic component modules (or units) incorporated therein. A consumer product comprising an OLED that includes the compound of the present disclosure in the organic layer in the OLED is disclosed. Such consumer products would include any kind of products that include one or more light source(s) and/or one or more of some type of visual displays. Some examples of such consumer products include flat panel displays, curved displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads-up displays, fully or partially transparent displays, flexible displays, rollable displays, foldable displays, stretchable displays, laser printers, telephones, mobile phones, tablets, phablets, personal digital assistants (PDAs), wearable devices, laptop computers, digital cameras, camcorders, viewfinders, micro-displays (displays that are less than 2 inches diagonal), 3-D displays, virtual reality or augmented reality displays, vehicles, video walls comprising multiple displays tiled together, theater or stadium screen, a light therapy device, and a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.), but could be used outside this temperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms “halo,” “halogen,” or “halide” as used interchangeably and refer to fluorine, chlorine, bromine, and iodine.

The term “acyl” refers to a substituted carbonyl radical (C(O)—R_(s)).

The term “ester” refers to a substituted oxycarbonyl (—O—C(O)—R_(s) or —C(O)—O—R_(s)) radical.

The term “ether” refers to an —OR_(s) radical.

The terms “sulfanyl” or “thio-ether” are used interchangeably and refer to a —SR_(s) radical.

The term “sulfinyl” refers to a —S(O)—R_(s) radical.

The term “sulfonyl” refers to a —SO₂—R_(s) radical.

The term “phosphino” refers to a —P(R_(s))₃ radical, wherein each R_(s) can be same or different. The term “silyl” refers to a —Si(R_(s))₃ radical, wherein each R can be same or different.

In each of the above, R_(s) can be hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, and combination thereof. Preferred R_(s) is selected from the group consisting of alkyl, cycloalkyl, aryl, heteroaryl, and combination thereof.

The term “alkyl” refers to and includes both straight and branched chain alkyl radicals. Preferred alkyl groups are those containing from one to fifteen carbon atoms and includes methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl,and the like. Additionally, the alkyl group may be optionally substituted.

The term “cycloalkyl” refers to and includes monocyclic, polycyclic, and spiro alkyl radicals. Preferred cycloalkyl groups are those containing 3 to 12 ring carbon atoms and includes cyclopropyl, cyclopentyl, cyclohexyl, bicyclo[3.1.1]heptyl, spiro[4.5]decyl, spiro[5.5]undecyl, adamantyl, and the like. Additionally, the cycloalkyl group may be optionally substituted.

The terms “heteroalkyl” or “heterocycloalkyl” refer to an alkyl or a cycloalkyl radical, respectively, having at least one carbon atom replaced by a heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si and Se, preferably, O, S or N. Additionally, the heteroalkyl or heterocycloalkyl group is optionally substituted.

The term “alkenyl” refers to and includes both straight and branched chain alkene radicals. Alkenyl groups are essentially alkyl groups that include at least one carbon-carbon double bond in the alkyl chain Cycloalkenyl groups are essentially cycloalkyl groups that include at least one carbon-carbon double bond in the cycloalkyl ring. The term “heteroalkenyl” as used herein refers to an alkenyl radical having at least one carbon atom replaced by a heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si and Se, preferably, O, S or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl, cycloalkenyl, or heteroalkenyl group is optionally substituted.

The term “alkynyl” refers to and includes both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group is optionally substituted.

The terms “aralkyl” or “arylalkyl” are used interchangeably and refer to an alkyl group that is substituted with an aryl group. Additionally, the aralkyl group is optionally substituted.

The term “heterocyclic group” refers to and includes aromatic and non-aromatic cyclic radicals containing at least one heteroatom. Optionally the at least one heteroatom is selected from O, S, N, P, B, Si and Se, preferably, O, S or N. Hetero-aromatic cyclic radicals may be used interchangeably with heteroaryl. Preferred hetero-non-aromatic cyclic groups are those containing 3 to 7 ring atoms which includes at least one hetero atom, and includes cyclic amines such as morpholino, piperidino, pyrrolidino, and the like, and cyclic ethers/thio-ethers, such as tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, and the like. Additionally, the heterocyclic group may be optionally substituted.

The term “aryl” refers to and includes both single-ring aromatic hydrocarbyl groups and polycyclic aromatic ring systems. The polycyclic rings may have two or more rings in which two carbons are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is an aromatic hydrocarbyl group, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred aryl groups are those containing six to thirty carbon atoms, preferably six to twenty carbon atoms, more preferably six to twelve carbon atoms. Especially preferred is an aryl group having six carbons, ten carbons or twelve carbons. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, triphenyl, triphenylene, fluorene, and naphthalene. Additionally, the aryl group may be optionally substituted.

The term “heteroaryl” refers to and includes both single-ring hetero-aromatic groups and polycyclic aromatic ring systems that include at least one heteroatom. The heteroatoms include, but are not limited to O, S, N, P, B, Si and Se. In many instances, O, S or N are the preferred heteroatoms. Hetero-single ring aromatic systems are preferably single rings with 5 or 6 ring atoms, and the ring can have from one to six heteroatoms. The hetero-polycyclic ring systems can have two or more rings in which two atoms are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is a heteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. The hetero-polycyclic aromatic ring systems can have from one to six heteroatoms per ring of the polycyclic aromatic ring system. Preferred heteroaryl groups are those containing three to thirty carbon atoms, preferably three to twenty carbon atoms, more preferably three to twelve carbon atoms. Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, preferably dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and aza-analogs thereof. Additionally, the heteroaryl group may be optionally substituted.

Of the aryl and heteroaryl groups listed above, the groups of triphenylene, naphthalene, anthracene, dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, pyrazine, pyrimidine, triazine, and benzimidazole, and the respective aza-analogs of each thereof are of particular interest.

The terms alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aralkyl, heterocyclic group, aryl, and heteroaryl, as used herein, are independently unsubstituted or substituted with one or more general substituents.

In many instances, the general substituents are selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In some instances, the preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

In some instances, the preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, alkoxy, aryloxy, amino, silyl, aryl, heteroaryl, sulfanyl, and combinations thereof.

In yet other instances, the more preferred general substituents are selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, aryl, heteroaryl, and combinations thereof.

The terms “substituted” and “substitution” refer to a substituent other than H that is bonded to the relevant position, e.g., a carbon or nitrogen. For example, when R¹ represents mono-substitution, then one R¹ must be other than H (i.e., a substitution) Similarly, when R¹ represents di-substitution, then two of R¹ must be other than H Similarly, when R¹ represents no substitution, R¹, for example, can be a hydrogen for available valencies of ring atoms, as in carbon atoms for benzene and the nitrogen atom in pyrrole, or simply represents nothing for ring atoms with fully filled valencies, e.g., the nitrogen atom in pyridine. The maximum number of substitutions possible in a ring structure will depend on the total number of available valencies in the ring atoms.

As used herein, “combinations thereof” indicates that one or more members of the applicable list are combined to form a known or chemically stable arrangement that one of ordinary skill in the art can envision from the applicable list. For example, an alkyl and deuterium can be combined to form a partial or fully deuterated alkyl group; a halogen and alkyl can be combined to form a halogenated alkyl substituent; and a halogen, alkyl, and aryl can be combined to form a halogenated arylalkyl. In one instance, the term substitution includes a combination of two to four of the listed groups. In another instance, the term substitution includes a combination of two to three groups. In yet another instance, the term substitution includes a combination of two groups. Preferred combinations of substituent groups are those that contain up to fifty atoms that are not hydrogen or deuterium, or those which include up to forty atoms that are not hydrogen or deuterium, or those that include up to thirty atoms that are not hydrogen or deuterium. In many instances, a preferred combination of substituent groups will include up to twenty atoms that are not hydrogen or deuterium.

The “aza” designation in the fragments described herein, i.e. aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more of the C-H groups in the respective aromatic ring can be replaced by a nitrogen atom, for example, and without any limitation, azatriphenylene encompasses both dibenzo[fh]quinoxaline and dibenzo[fh]quinoline. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.

As used herein, “deuterium” refers to an isotope of hydrogen. Deuterated compounds can be readily prepared using methods known in the art. For example, U.S. Pat. No. 8,557,400, Patent Pub. No. WO 2006/095951, and U.S. Pat. Application Pub. No. US 2011/0037057, which are hereby incorporated by reference in their entireties, describe the making of deuterium-substituted organometallic complexes. Further reference is made to Ming Yan, et al., Tetrahedron 2015, 71, 1425-30 and Atzrodt et al., Angew. Chem. Int. Ed. (Reviews) 2007, 46, 7744-65, which are incorporated by reference in their entireties, describe the deuteration of the methylene hydrogens in benzyl amines and efficient pathways to replace aromatic ring hydrogens with deuterium, respectively.

It is to be understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it were a fragment (e.g. phenyl, phenylene, naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. benzene, naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or attached fragment are considered to be equivalent.

In some instance, a pair of adjacent substituents can be optionally joined or fused into a ring. The preferred ring is a five, six, or seven-membered carbocyclic or heterocyclic ring, includes both instances where the portion of the ring formed by the pair of substituents is saturated and where the portion of the ring formed by the pair of substituents is unsaturated. As used herein, “adjacent” means that the two substituents involved can be on the same ring next to each other, or on two neighboring rings having the two closest available substitutable positions, such as 2,2′ positions in a biphenyl, or 1,8 position in a naphthalene, as long as they can form a stable fused ring system.

In one aspect, the present invention includes a compound of Formula I:

wherein:

-   -   ring B is a 5-membered heterocyclic ring, or a 6-membered         carbocyclic ring;     -   each of X¹ and X² is independently C, CR, or N, with at least         one of them being C;     -   each of X³-X¹¹ is independently C, CR, or N, with at least one         of them being N, and two adjacent of X³-X⁷ are carbon-fused to         the shown moiety through the linkage indicated by the two         squiggly lines;     -   Y is selected from the group consisting of O, S, Se, NR′, CR′R″,         and SiR′R″;     -   each of R^(A) and R^(B) independently represents zero, mono, or         up to a maximum allowed substitution to its associated ring;     -   each of R, R′, R″, R^(A), and R^(B) is independently a hydrogen         or a substituent selected from the group consisting of —SiR¹R²R³         or —GeR¹R²R³, deuterium, halogen, alkyl, cycloalkyl,         heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy,         amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl,         alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester,         nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino,         and combinations thereof, with at least one of R^(A) or R^(B)         comprising —SiR¹R²R³ or —GeR¹R²R³;     -   each of R¹, R², and R³ is independently selected from the group         consisting of alkyl, aryl group, heteroaryl group, and         combinations thereof; and     -   any two substituents are optionally joined or fused to form a         ring where chemically feasible.

In one embodiment, each of R, R′, R″, R^(A) , and R^(B) is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

In one embodiment, at least one of R^(A) or R^(B) is —SiR¹R²R³.

In one embodiment, each of R¹, R², and R³ is independently an aryl group or heteroaryl group. In one embodiment, at least one of R¹, R², and R³ comprises a carbazole or aza-carbazole

group.

In one embodiment, X¹ and X² are each independently C and ring B is a 6-membered aromatic ring.

In one embodiment, X¹ and X² are each independently C and ring B is a benzene ring.

In one embodiment, two adjacent R^(B) substituents of ring B are further joined to form a fused ring.

In one embodiment, the fused ring is a 5-membered ring.

In one embodiment, the fused ring is an imidazole or a pyrrole ring.

In one embodiment, X¹ and X² are each independently C and ring B is a 5-membered heteroaryl ring.

In one embodiment, the 5-membered heteroaryl ring is a pyrrole ring.

In one embodiment, two adjacent R^(B) substituents of the 5-membered heteroaryl ring are further joined to form a fused ring.

In one embodiment, the fused ring is a 6-membered aromatic ring.

In one embodiment, X¹ is N and X² is C.

In one embodiment, ring B is an imidazole ring.

In one embodiment, two R^(B) groups are joined together to form a fused 6-membered aromatic ring.

In one embodiment, the 6-membered aromatic ring is a benzene ring.

In one embodiment, X³-X¹¹ are each independently C.

In one embodiment, one of X³-X⁷ is N.

In one embodiment, one of X⁸-X¹¹ is N.

In one embodiment, R^(A) for each occurrence is independently hydrogen.

In one embodiment, R^(A) for each occurrence is independently hydrogen, deuterium, alkyl, cycloalkyl, aryl, heteroaryl, or combinations thereof.

In one embodiment, Y is selected from the group consisting of O and S.

In one embodiment, the compound is selected from the group consisting of

wherein:

-   -   R^(D) independently represents zero, mono, or up to a maximum         allowed substitution to its associated ring;     -   R^(D) for each occurrence is independently a hydrogen or a         substituent selected from the group consisting of —SiR¹R²R³ or         —GeR¹R²R³, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,         heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,         boryl, borate, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,         aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile,         isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and         combinations thereof;

Y_(A) for each occurrence is independently selected from the group consisting of BR_(e), NR_(e), PR_(e), O, S, Se, C═O, S═O, SO₂, CR_(e)R_(f), SiR_(e)R_(f), and GeR_(e)R_(f);

wherein R_(e) and R_(f) are optionally fused or joined to form a ring;

each of R_(e) and R_(f) is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

any two substituents are optionally joined or fused to form a ring where chemically feasible; and

R^(A), R^(B), X³-X¹¹, and Y are all defined the same as above.

In one embodiment, the compound is selected from the group consisting of Formulas 1-69:

wherein R₁, R₂, R₃, and R₄ are selected from the group consisting of R1-R50:

and wherein Ar for each occurrence is independently selected from the group consisting of A1-A200:

In another aspect, the invention includes an organic light emitting device (OLED) comprising an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the wherein the organic layer comprises a compound according to Formula I.

In one embodiment, wherein the organic layer is an emissive layer and the compound according to Formula I is a host.

In some embodiments, the OLED has one or more characteristics selected from the group consisting of being flexible, being rollable, being foldable, being stretchable, and being curved. In some embodiments, the OLED is transparent or semi-transparent. In some embodiments, the OLED further comprises a layer comprising carbon nanotubes.

In some embodiments, the OLED further comprises a layer comprising a delayed fluorescent emitter. In some embodiments, the OLED comprises a RGB pixel arrangement or white plus color filter pixel arrangement. In some embodiments, the OLED is a mobile device, a hand held device, or a wearable device. In some embodiments, the OLED is a display panel having less than 10 inch diagonal or 50 square inch area. In some embodiments, the OLED is a display panel having at least 10 inch diagonal or 50 square inch area. In some embodiments, the OLED is a lighting panel.

The emitter dopants can be phosphorescent dopants and/or fluorescent dopants. The organic layer can include a compound according to Formula I, and its variations as described herein as a host.

In one embodiment, the organic layer further comprises a phosphorescent emissive dopant; wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein:

-   -   each Y¹ to Y¹³ are independently selected from the group         consisting of carbon and nitrogen;     -   Y′ is selected from the group consisting of BR_(e), NR_(e),         PR_(e), O, S, Se, C═O, S═O, SO₂, CR_(e)R_(f), SiR_(e)R_(f), and         GeR_(e)R_(f);     -   R_(e) and R_(f) are optionally fused or joined to form a ring;     -   each of R_(a), R_(b), R_(c), and R_(d) independently represents         zero, mono, or up to a maximum allowed substitution to its         associated ring;     -   each of R_(a), R_(b), R_(c), R_(d), R_(e) and R_(f) is         independently hydrogen or a substituent selected from the group         consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl,         arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, borate,         alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,         acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile,         sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations         thereof; and     -   any two adjacent R_(a), R_(b), R_(c), and R_(d) groups are         optionally fused or joined to form a ring or form a multidentate         ligand.

In one embodiment, the organic layer is a blocking layer and the compound according to Formula I is a blocking material in the organic layer.

In one embodiment, the organic layer is a transporting layer and a compound according to Formula I is a transporting material in the organic layer.

In one embodiment, the compound is an acceptor, and the OLED further comprises a sensitizer selected from the group consisting of a delayed fluorescence emitter, a phosphorescent emitter, and combination thereof.

In one embodiment, the compound is a fluorescent emitter, a delayed fluorescence emitter, or a component of an exciplex that is a fluorescent emitter or a delayed fluorescence emitter.

In one embodiment, the compound is a sensitizer, and the OLED further comprises an acceptor selected from the group consisting of a fluorescent emitter, a delayed fluorescence emitter, and combination thereof. The sensitizer can be the compound itself, or an exciplex of which the compound is one of the components.

According to another aspect, a formulation comprising the compound described herein is also disclosed.

The OLED disclosed herein can be incorporated into one or more of a consumer product, an electronic component module, and a lighting panel.

In yet another aspect of the present disclosure, a formulation that comprises the novel compound disclosed herein is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, electron blocking material, hole blocking material, and an electron transport layer material, disclosed herein.

The present disclosure encompasses any chemical structure comprising the novel compound of the present disclosure, or a monovalent or polyvalent variant thereof. In other words, the inventive compound, or a monovalent or polyvalent variant thereof, can be a part of a larger chemical structure. Such chemical structure can be selected from the group consisting of a monomer, a polymer, a macromolecule, and a supramolecule (also known as supermolecule). As used herein, a “monovalent variant of a compound” refers to a moiety that is identical to the compound except that one hydrogen has been removed and replaced with a bond to the rest of the chemical structure. As used herein, a “polyvalent variant of a compound” refers to a moiety that is identical to the compound except that more than one hydrogen has been removed and replaced with a bond or bonds to the rest of the chemical structure. In the instance of a supramolecule, the inventive compound can also be incorporated into the supramolecule complex without covalent bonds.

Combination With Other Materials

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

Conductivity Dopants:

A charge transport layer can be doped with conductivity dopants to substantially alter its density of charge carriers, which will in turn alter its conductivity. The conductivity is increased by generating charge carriers in the matrix material, and depending on the type of dopant, a change in the Fermi level of the semiconductor may also be achieved. Hole-transporting layer can be doped by p-type conductivity dopants and n-type conductivity dopants are used in the electron-transporting layer.

Non-limiting examples of the conductivity dopants that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: EP01617493, EP01968131, EP2020694, EP2684932, US20050139810, US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455, WO2009008277, WO2009011327, WO2014009310, US2007252140, US2015060804, US20150123047, and US2012146012.

HIL/HTL:

A hole injecting/transporting material to be used in the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but are not limited to: a phthalocyanine or porphyrin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and silane derivatives; a metal oxide derivative, such as MoO_(x); a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, but are not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; the group consisting of aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and the group consisting of 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Each Ar may be unsubstituted or may be substituted by a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the group consisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH) or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are not limited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40; (Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independently selected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In another aspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect, Met is selected from Ir, Pt, Os, and Zn. In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fe/Fc couple less than about 0.6 V.

Non-limiting examples of the HIL and HTL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN102702075, DE102012005215, EP01624500, EP01698613, EP01806334, EP01930964, EP01972613, EP01997799, EP02011790, EP02055700, EP02055701, EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765, JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473, TW201139402, US06517957, US20020158242, US20030162053, US20050123751, US20060182993, US20060240279, US20070145888, US20070181874, US20070278938, US20080014464, US20080091025, US20080106190, US20080124572, US20080145707, US20080220265, US20080233434, US20080303417, US2008107919, US20090115320, US20090167161, US2009066235, US2011007385, US20110163302, US2011240968, US2011278551, US2012205642, US2013241401, US20140117329, US2014183517, US5061569, US5639914, WO05075451, WO07125714, WO08023550, WO08023759, WO2009145016, WO2010061824, WO2011075644, WO2012177006, WO2013018530, WO2013039073, WO2013087142, WO2013118812, WO2013120577, WO2013157367, WO2013175747, WO2014002873, WO2014015935, WO2014015937, WO2014030872, WO2014030921, WO2014034791, WO2014104514, WO2014157018,

EBL:

An electron blocking layer (EBL) may be used to reduce the number of electrons and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies, and/or longer lifetime, as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and/or higher triplet energy than the emitter closest to the EBL interface. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and/or higher triplet energy than one or more of the hosts closest to the EBL interface. In one aspect, the compound used in EBL contains the same molecule or the same functional groups used as one of the hosts described below.

Additional Hosts:

The light emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as light emitting dopant material, and may contain one or more additional host materials using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant. Any host material may be used with any dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have the following general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴ are independently selected from C, N, O, P, and S; L¹⁰¹ is an another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O-N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, Met is selected from Ir and Pt. In a further aspect, (Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

In one aspect, the host compound contains at least one of the following groups selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each group is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, host compound contains at least one of the following groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. k is an integer from 0 to 20 or 1 to 20. X¹⁰¹ to X¹⁰⁸ are independently selected from C (including CH) or N. Z¹⁰¹ and Z¹⁰² are independently selected from NR¹⁰¹, O, or S.

Non-limiting examples of the additional host materials that may be used in an OLED in combination with the host compound disclosed herein are exemplified below together with references that disclose those materials: EP2034538, EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644, KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919, US20060280965, US20090017330, US20090030202, US20090167162, US20090302743, US20090309488, US20100012931, US20100084966, US20100187984, US2010187984, US2012075273, US2012126221, US2013009543, US2013105787, US2013175519, US2014001446, US20140183503, US20140225088, US2014034914, US7154114, WO2001039234, WO2004093207, WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754, WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778, WO2009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423, WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649, WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472, US20170263869, US20160163995, US9466803.

Emitter:

An emitter example is not particularly limited, and any compound may be used as long as the compound is typically used as an emitter material. Examples of suitable emitter materials include, but are not limited to, compounds which can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence; see, e.g., U.S. application Ser. No. 15/700,352, which is hereby incorporated by reference in its entirety), triplet-triplet annihilation, or combinations of these processes. In some embodiments, the emissive dopant can be a racemic mixture, or can be enriched in one enantiomer.

Non-limiting examples of the emitter materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526, EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907, EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652, KR20120032054, KR20130043460, TW201332980, US06699599, US06916554, US20010019782, US20020034656, US20030068526, US20030072964, US20030138657, US20050123788, US20050244673, US2005123791, US2005260449, US20060008670, US20060065890, US20060127696, US20060134459, US20060134462, US20060202194, US20060251923, US20070034863, US20070087321, US20070103060, US20070111026, US20070190359, US20070231600, US2007034863, US2007104979, US2007104980, US2007138437, US2007224450, US2007278936, US20080020237, US20080233410, US20080261076, US20080297033, US200805851, US2008161567, US2008210930, US20090039776, US20090108737, US20090115322, US20090179555, US2009085476, US2009104472, US20100090591, US20100148663, US20100244004, US20100295032, US2010102716, US2010105902, US2010244004, US2010270916, US20110057559, US20110108822, US20110204333, US2011215710, US2011227049, US2011285275, US2012292601, US20130146848, US2013033172, US2013165653, US2013181190, US2013334521, US20140246656, US2014103305, U.S. Pat. Nos. 6,303,238, 6,413,656, 6,653,654, 6,670,645, 6,687,266, 6,835,469, 6,921,915, 7,279,704, 7,332,232, 7,378,162, 7,534,505, 7,675,228, 7,728,137, 7,740,957, 7,759,489, 7,951,947, 8,067,099, 8,592,586, 8,871,361, WO06081973, WO06121811, WO07018067, WO07108362, WO07115970, WO07115981, WO08035571, WO2002015645, WO2003040257, WO2005019373, WO2006056418, WO2008054584, WO2008078800, WO2008096609, WO2008101842, WO2009000673, WO2009050281, WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO2010118029, WO2011044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471, WO2013094620, WO2013107487, WO2013174471, WO2014007565, WO2014008982, WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450,

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies and/or longer lifetime as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than the emitter closest to the HBL interface. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than one or more of the hosts closest to the HBL interface.

In one aspect, compound used in HBL contains the same molecule or the same functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ is an integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

In one aspect, compound used in ETL contains at least one of the following groups in the

molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. Ar¹ to Ar³ has the similar definition as Ar's mentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selected from C (including CH) or N.

In another aspect, the metal complexes used in ETL include, but are not limited to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

Non-limiting examples of the ETL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103508940, EP01602648, EP01734038, EP01956007, JP2004-022334, JP2005149918, JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977, US2007018155, US20090101870, US20090115316, US20090140637, US20090179554, US2009218940, US2010108990, US2011156017, US2011210320, US2012193612, US2012214993, US2014014925, US2014014927, US20140284580, U.S. Pat. Nos. 6,656,612, 8,415,031, WO2003060956, WO2007111263, WO2009148269, WO2010067894, WO2010072300, WO2011074770, WO2011105373, WO2013079217, WO2013145667, WO2013180376, WO2014104499, WO2014104535,

Charge Generation Layer (CGL)

In tandem or stacked OLEDs, the CGL plays an essential role in the performance, which is composed of an n-doped layer and a p-doped layer for injection of electrons and holes, respectively. Electrons and holes are supplied from the CGL and electrodes. The consumed electrons and holes in the CGL are refilled by the electrons and holes injected from the cathode and anode, respectively; then, the bipolar currents reach a steady state gradually. Typical CGL materials include n and p conductivity dopants used in the transport layers.

In any above-mentioned compounds used in each layer of the OLED device, the hydrogen atoms can be partially or fully deuterated. Thus, any specifically listed substituent, such as, without limitation, methyl, phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, classes of substituents such as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also encompass undeuterated, partially deuterated, and fully deuterated versions thereof.

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting.

Experimental Data Synthesis of Compound A

Synthesis of 1-(3-Bromo-9H-carbazol-9-yl)benzo[4,5]thieno [2,3-c]pyridine

1-Chlorobenzo[4,5]thieno[2,3-c]pyridine (6.59 g, 30.0 mmol), 3-bromo-9H-carbazole (11.1 g, 45.1 mmol) and caesium carbonate (14.7 g, 45.1 mmol) were suspended in dry DMSO (150 mL) and stirred at 140 ° C. under nitrogen for 22 h. The reaction was cooled to RT, quenched with water (100 mL) and extracted with CH₂Cl₂ (3×50 mL). The combined organic layers were washed with brine (25 ml), dried over MgSO₄, filtered and concentrated. The crude was adsorbed onto silica gel and purified by flash column chromatography (silica gel, 330 g cart., 0-20% EtOAc/isohexane). The impure product obtained was suspended in CH₂Cl₂ and filtered. The filtrate was concentrated, adsorbed onto silica gel and purified by flash column chromatography (silica gel, 330 g cart., 0-100% CH₂Cl₂/isohexane) giving 1-(3-bromo-9H-carbazol-9-yl)benzo[4,5]thieno[2,3-c]pyridine (7.25 g, 16.2 mmol, 54% yield) as a white foamy solid.

Synthesis of 1-(3-(Triphenylsilyl)-9H-carbazol-9-yl)benzo[4,5]thieno[2,3-c]pyridine (Compound A)

n-Butyllithium (2.15 M in hexanes, 4.2 mL, 9 0 mmol) was added quickly to a stirred solution of 1-(3-bromo-9H-carbazol-9-yl)benzo[4,5]thieno[2,3-c]pyridine (3.71 g, 8.64 mmol) in THF (32 mL) under nitrogen at −40 ° C. and stirred at this temperature for 15 min. Triphenylchlorosilane (7.88 g, 26.7 mmol) in THF (11 mL) was added quickly and the reaction mixture was left to warm to RT and stirred for 18 h. The reaction was quenched with water (50 mL) and extracted with EtOAc (3×30 mL). The combined organic layers were dried over MgSO₄, filtered and concentrated. The crude was purified by acidic reverse phase column chromatography (220 g C18 column, 50-100% MeCN in 0.1% aqueous formic acid). The obtained product was triturated with hot MeCN to give 1-(3-(triphenylsilyl)-9H-carbazol-9-yl)benzo[4,5]thieno[2,3-c]pyridine (Compound A) (2.42 g, 3.74 mmol, 43% yield,) as a white solid.

Synthesis of Compound B

Synthesis of 1-[3-(Methoxy-diphenyl-silanyl)-carbazol-9-yl]benzo[4,5]thieno[2,3-c]pyridine

To a stirred solution of 1-(3-Bromo-carbazol-9-yl)-benzo[4,5]thieno[2,3-c]pyridine (10.8, 25.2 mmol) in THF (200 mL) was adeed ^(n)Butyl lithium (2.5 M, 12.07 mL, 30.2 mmol), at −78° C. under N₂. The reaction mixture was then stirred at same temperature for 1 h. Dimethoxy-diphenyl-silane (8.95 mL, 37.7 mmol) was dissolved in THF (30 mL) and added to reaction mixture slowly for 15 min. The reaction mixture was raised slowly to the room temperature and stir it for overnight. Next day morning satd. NH₄Cl solution (50 mL) was added to the mixture and layers were separated. Aqueous layer was extracted with EtOAc (3×200 mL and all organics were dried over Na₂SO₄ and evaporated on rotary vacuo. Performed silica gel column chromatography to remove de-brominated 1-(9H-carbazol-9-yl)benzo[4,5]thieno[2,3-c]pyridine using 50% DCM/Heptanes and then collected desired product (1-[3-(Methoxy-diphenyl-silanyl)-carbazol-9-yl]-benzo[4,5]thieno[2,3-c]pyridine, 7 g, 50%) using 50% EtOAc/Heptanes.

Synthesis of 1-{3-[(3-Chloro-phenyl)-diphenyl-silanyl]-carbazol-9-yl}-benzo[4,5]thieno[2,3-c]pyridine

To a stirred solution of 1-Bromo-3-chloro-benzene (2.0 mL, 17.41 mmol) in diethyl ether (200 mL) was adeed ^(n)Butyl lithium (2.5 M, 7 mL, 17.41 mmol), at −78° C. under N₂. The reaction mixture was then attired at same temperature for 1 h. 1[3-(Methoxy-diphenyl-silanyl)-carbazol-9-yl]-benzo[4,5]thieno[2,3-c]pyridine (7 g, 12.44 mmol) was dissolved in diethyl ether (70 mL) and added to reaction mixture slowly for 15 min. The reaction mixture was raised slowly to the room temperature and stir it for overnight. Saturated NH₄Cl solution (30 mL) was added to the mixture and layers were separated. Aqueous layer was extracted with EtOAc (3×150 mL and all organics were dried over Na₂SO₄, evaporated on rotary vacuo and purified by column using 60% DCM/Heptanes to give the desired product 1-{3-[(3-Chloro-phenyl)-diphenyl-silanyl]-carbazol-9-yl}-benzo[4,5]thieno[2,3-c]pyridine (5.62 g, 70% yield).

Synthesis of 1-{3-[(3-Chloro-phenyl)-diphenyl-silanyl]-carbazol-9-yl}-benzo[4,5]thieno[2,3-c]pyridine (Compound B)

1-{3-[(3 -Chloro-phenyl)-diphenyl-silanyl]-carbazol-9-yl}-benzo[4,5]thieno[2,3 -c]pyridine, (5.62 g, 8.74 mmol), carbazole (2.92, 17.47 mmol), Di-tert-butyl(2,2-diphenyl-1-methyl-1-cyclopropyl)phosphine (c-BRIDP) (616 mg, 1.747 mmol), ally palladium chloride dimer (176 mg, 0.481 mmol), and sodium tert-butoxide (2.52 g, 26.2 mmol), in 120 mL of toluene were degassed with N₂ for 15 min. and refluxed at 110° C. for overnight. Reaction was carried out in a 500 mL pressure round bottom flask. Reaction mixture was cooled to room temperature, removed toluene using rotary vacuo, and filtered through Celite pad, washed thoroughly with EtOAc (150 mL) until no starting material was observed in TLC. Removed all organic solvents on rotary vacuo and purified by column using 40% EtOAc/Heptanes to give the desired product 1-{3-[(3-Carbazol-9-yl-phenyl)-diphenyl-silanyl]-carbazol-9-yl}-benzo[4,5]thieno[2,3-c]pyridine (Compound B) (6.5 g, 95% yield).

Device Compounds:

Device Example 1:

OLEDs were grown on a glass substrate pre-coated with an indium-tin-oxide (ITO) layer having a sheet resistance of 15-Ω/sq. Prior to any organic layer deposition or coating, the substrate was degreased with solvents and then treated with an oxygen plasma for 1.5 minutes with 50W at 100 mTorr and with UV ozone for 5 minutes. The devices in Table 1 were fabricated in high vacuum (<10⁻⁶ Torr) by thermal evaporation. The anode electrode was 750 Å of indium tin oxide (ITO). The device example had organic layers consisting of, sequentially, from the ITO surface, 100 Å thick Compound 1 (HIL), 250 Å layer of Compound 2 (HTL), 50 Å of Compound 3(EBL), 300Å of Compound 3 doped with 20% Compound B and 20% Emitter 1 (EML), 50 Å of Compound B (BL), 300 Å of Compound 4 doped with 35% of Compound 5 (ETL), 10 Å of Compound 5 (EIL) followed by 1,000 Å of Al (Cath). All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1ppm of H₂ O and O₂, ) immediately after fabrication with a moisture getter incorporated inside the package. Doping percentages are in volume percent.

The device data for Device Example 1 is summarized in Table 1, below.

TABLE 1 At 1000 cd/m² 1931 CIE Em_(max) Voltage LE EQE PE Device x y [nm] (V) [cd/A] [%] [Lm/W] Example 1 0.179 0.409 475 4.2 63.0 26.7 46.7 

1.-37. (canceled)
 38. A compound of Formula I:

wherein: ring B is a 5-membered heterocyclic ring, or a 6-membered carbocyclic ring; each of X¹ and X² is independently C, CR, or N, with at least one of them being C; each of X³-X¹¹ is independently C, CR, or N, with at least one of them being N, and two adjacent of X³-X⁷ are carbon-fused to the shown moiety through the linkage indicated by the two squiggly lines; Y is selected from the group consisting of O, S, Se, NR′, CR′R″, and SiR′R″; each of R^(A) and R^(B) independently represents zero, mono, or up to a maximum allowed substitution to its associated ring; each of R, R′, R″, R″, R^(A), and R^(B) is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³ or —GeR¹R²R³, deuterium, halogen, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, nitrile, and combinations thereof, with at least one of R^(A) or R^(B) comprising —SiR¹R²R³ or —GeR¹R²R³; each of R¹, R², and R³ is independently selected from the group consisting of alkyl, aryl group, heteroaryl group, and combinations thereof; and any two substituents are optionally joined or fused to form a ring.
 39. The compound of claim 38, wherein each of R, R′, R″, R^(A) , and R^(B) is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³, deuterium, F, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, nitrile, and combinations thereof.
 40. The compound of claim 38, wherein at least one of R^(A) or R^(B) is —SiR¹R²R³.
 41. The compound of claim 38, wherein each of R¹, R², and R³ is independently an aryl group or heteroaryl group.
 42. The compound of claim 38, wherein at least one of R¹, R², and R³ comprises a carbazole or aza-carbazole group.
 43. The compound of claim 38, wherein X¹ and X² are each independently C and ring B is a 6-membered aromatic ring.
 44. The compound of claim 43, two adjacent R^(B) substituents of ring B are further joined to form a fused ring.
 45. The compound of claim 38, wherein X¹ and X² are each independently C and ring B is a 5-membered heteroaryl ring; or wherein X¹ is N and X² is C.
 46. The compound of claim 38, wherein X³-X¹¹ are each independently C; or wherein one of X³-X¹¹ is N.
 47. The compound of claim 38, wherein R^(A) for each occurrence is independently hydrogen, deuterium, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, or combinations thereof. ; and/or wherein R^(B) for each occurrence is independently hydrogen, deuterium, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, or combinations thereof.
 48. The compound of claim 38, wherein Y is selected from the group consisting of O and S.
 49. The compound of claim 38, wherein the compound is selected from the group consisting of:

wherein: R^(D) independently represents zero, mono, or up to a maximum allowed substitution to its associated ring; R^(D) for each occurrence is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³ or —GeR¹R²R³, deuterium, halogen, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, nitrile, and combinations thereof; Y_(A) for each occurrence is independently selected from the group consisting of BR_(e), NR_(e), PR_(e), O, S, Se, C═O, S═O, SO₂, CR_(e)R_(f), SiR_(e)R_(f), and GeR_(e)R_(f); wherein R_(e) and R_(f) are optionally fused or joined to form a ring; each of R_(e) and R_(f) is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; any two substituents are optionally joined or fused to form a ring; and R^(A), R^(B), X³-X¹¹, and Y are each as defined in claim
 1. 50. An organic light emitting device (OLED) comprising: an anode; a cathode; and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a compound of Formula I:

wherein: ring B is a 5-membered heterocyclic ring, or a 6-membered carbocyclic ring; each of X¹ and X² is independently C, CR, or N, with at least one of them being C; each of X³-X¹¹ is independently C, CR, or N, with at least one of them being N, and two adjacent of X³-X⁷ are carbon-fused to the shown moiety through the linkage indicated by the two squiggly lines; Y is selected from the group consisting of O, S, Se, NR′, CR′R″, and SiR′R″; each of R^(A) and R^(B) independently represents zero, mono, or up to a maximum allowed substitution to its associated ring; each of R, R′, R″, R^(A), and R^(B) is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³ or —GeR¹R²R³, deuterium, halogen, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, nitrile, and combinations thereof, with at least one of R^(A) or R^(B) comprising —SiR¹R²R³ or —GeR¹R²R³; each of R¹, R², and R³ is independently selected from the group consisting of alkyl, aryl group, heteroaryl group, and combinations thereof; and any two substituents are optionally joined or fused to form a ring where chemically feasible.
 51. The OLED of claim 50, wherein the organic layer is an emissive layer and the compound of Formula I is a host.
 52. The OLED of claim 51, wherein the organic layer further comprises a phosphorescent emissive dopant; wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein: each Y¹ to Y¹³ are independently selected from the group consisting of carbon and nitrogen; Y′ is selected from the group consisting of BR_(e), NR_(e), PR_(e), O, S, Se, C═O, S═O, SO₂, CR_(e)R_(f), SiR_(e)R_(f), and GeR_(e)R_(f); R_(e) and R_(f) are optionally fused or joined to form a ring; each of R_(a), R_(b), R_(c), and R_(d) independently represents zero, mono, or up to a maximum allowed substitution to its associated ring; each of R_(a), R_(b), R_(c), R_(d), R_(e) and R_(f) is independently hydrogen or a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, borate, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and any two adjacent R_(a), R_(b), R_(c), and R_(d) groups are optionally fused or joined to form a ring or form a multidentate ligand.
 53. The OLED of claim 50, wherein the organic layer is a blocking layer and the compound of Formula I is a blocking material in the organic layer.
 54. A consumer product comprising an organic light-emitting device (OLED) comprising: an anode; a cathode; and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a compound according of Formula I:

wherein: ring B is a 5-membered heterocyclic ring, or a 6-membered carbocyclic ring; each of X¹ and X² is independently C, CR, or N, with at least one of them being C; each of X³-X¹¹ is independently C, CR, or N, with at least one of them being N, and two adjacent of X³-X⁷ are carbon-fused to the shown moiety through the linkage indicated by the two squiggly lines; Y is selected from the group consisting of O, S, Se, NR′, CR′R″, and SiR′R″; each of R^(A) and R^(B) independently represents zero, mono, or up to a maximum allowed substitution to its associated ring; each of R, R′, R″, R^(A), and R^(B) is independently a hydrogen or a substituent selected from the group consisting of —SiR¹R²R³ or —GeR¹R²R³, deuterium, halogen, alkyl, partially or fully deuterated alkyl, cycloalkyl, partially or fully deuterated cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, partially or fully deuterated aryl, heteroaryl, partially or fully deuterated heteroaryl, nitrile, and combinations thereof, with at least one of R^(A) or R^(B) comprising —SiR¹R²R³ or —GeR¹R²R³; each of R¹, R², and R³ is independently selected from the group consisting of alkyl, aryl group, heteroaryl group, and combinations thereof; and any two substituents are optionally joined or fused to form a ring where chemically feasible.
 55. The consumer product of claim 54, wherein the consumer product is selected from the group consisting of a flat panel display, a computer monitor, a medical monitor, a television, a billboard, a light for interior or exterior illumination and/or signaling, a heads-up display, a fully or partially transparent display, a flexible display, a laser printer, a telephone, a cell phone, tablet, a phablet, a personal digital assistant (PDA), a wearable device, a laptop computer, a digital camera, a camcorder, a viewfinder, a micro-display that is less than 2 inches diagonal, a 3-D display, a virtual reality or augmented reality display, a vehicle, a video walls comprising multiple displays tiled together, a theater or stadium screen, a light therapy device, and a sign.
 56. A formulation comprising a compound according to claim
 38. 